Plough reversing mechanism

ABSTRACT

Reversing mechanism, particularly for semi-reversible ploughs, where the reversing mechanism includes hydraulic reversing cylinders (10, 11). The reversing mechanism, or device (5) to be reversed, includes a lifting arm (8) which at its one end is rotatably supported at a point (9) which the reversing mechanism turns about, and which at its other end is fastened to the device (5) to be reversed. The reversing cylinders (10, 11) have approximately the same volume and approximately the same length of stroke and are affixed symmetrically to the lifting arm (8). The piston rods of the reversing cylinders (10, 11) are rotatably attached (15, 19) with one end of a pressure arm (17, 18) whose other end is rotatably fixed to the point (9) about which the reversing mechanism rotates. Each reversing cylinder (10, 11) is single-acting and arranged to turn the lifting arm (8) approximately 110 degrees from horizontal position before the reversing cylinder (10, 11) has attained full length of stroke and the piston rod of the non-activated reversing cylinder ( 11, 10) is brought to abut against the abutment screw (21, 16) and brake the remainder of the reversing operation, which takes place with the aid of gravity. Two identical double-acting hydraulic steering cylinders (24, 25) are connected in parallel with the reversing cylinders (10, 11) and are thus arranged automatically to adjust, for example, the back wheel (4) of a semi-reversible plough when the reversing mechanism is activated.

FIELD OF THE INVENTION

This invention concerns a reversing mechanism, particularly forsemi-reversible ploughs. Such ploughs usually have 4-8 double ploughshares fixed permanently or rotatably to a plough frame. The ploughframe is rotatably fixed to a carriage which at its front edge isarranged to be hung on the tractor's three-point mounting, and which atthe back is equipped with a back wheel which serves both as steeringwheel and depth wheel.

RELATED ART

Several disadvantages of the known semi-reversible ploughs relate to thereversing mechanism which turns the plough frame 180 degrees in thecarriage when the direction in which one is ploughing shall be swappedfrom left to right, or vice versa. The known reversing mechanisms ofthis type have one or two double-acting hydraulic cylinders which areattached to the plough carriage, to a tower on the carriage, or to aspecial arm which extends out from the carriage. These reversingmechanisms are characterized by having many, in part complicated,components, and by the outer measurements being large, so that thedistance between the tractor and plough is large, which brings with ittechnical ploughing disadvantages.

A good reversing mechanism of this kind must be able, inter alia, to usethe tractor hydraulics, turning the plough evenly and swiftly andpreventing the reversing mechanism from being exposed to large internalforces. Furthermore, the back wheel of the plough should be arranged tobe steered by hydraulic steering cylinders which are hydraulically tiedto the reversing mechanism in such a way that the back wheel isautomatically adjusted correctly upon reversal of the plough. Thereversal must also be stoppable at any point without pressure from theweight of the plough having an unfavourable effect on the steeringcylinders of the back wheel and moving these uncontrollably, causingpressure build-up in the hydraulic system.

SUMMARY OF THE INVENTION

The objective of this invention is to provide a reversing mechanism,particularly for semi-reversible ploughs, in which the above-mentioneddisadvantages are eliminated, and which at the same time satisfies theabove-mentioned requirements for a good reversing mechanism.

This objective is achieved by a reversing mechanism with the featuresstated in the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the execution of the invention is shown on the drawing,where:

FIG. 1 shows, from above, a semi-reversible plough with reversingmechanism according to the invention.

FIGS. 2, 3, 4 and 5 show in larger scale, from the front, the reversingmechanism at four stages of a reversing operation, and

FIG. 6 shows the hydraulic diagram for the reversing mechanism accordingto the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 reference no. 1 indicates the semi-reversible plough carriagewhich at the front is suspended from the three-point mounting 3 of atractor 2, and which at the back is equipped with a back wheel 4 whichserves both as steering wheel and depth wheel. A plough frame 5 to whichis rotatably attached a number of double plough shares 6 is arranged atthe back edge so as to be able to turn about a shaft 7 fastened to thecarriage 1. The uppermost lying plough share of the double plough shares6 is, for the sake of clarity, not drawn on the drawing. At its frontedge, the plough frame 5 is attached to one end of a lifting arm 8,whose other end is rotatably supported on a shaft 9 fastened tocarriage 1. As shown in FIG. 2, the plough frame 5 may, with the aid oftwo single-acting hydraulic reversing cylinders 10, 11 which arerotatably attached to lifting arm 8 and connected to the tractor 2hydraulics, be turned approximately 180 degrees to and fro about theshafts 7, 9 mentioned.

When plough frame 5 is to be turned from the working position as shownin FIG. 2 to the working position as shown in FIG. 5, pressure isapplied to cylinder 10 via hose 12, and cylinder 11 is connected forreturn to the tractor 2 hydraulics via hose 13. The force from cylinder10 acts via an abutment ring 14, which is rotatably attached to thecylinder 10 piston rod with aid of a bolt 15, against an abutment screw16 which is fixed to the carriage 1 and provides a moment which turnslifting arm 8, and thus the plough frame 5, about the shaft 9. Apressure arm 17, of which one end is rotatably supported on the cylinder10 piston rod with the aid of the bolt 15, is at its other end rotatablysupported on shaft 9. A corresponding pressure arm 18, one end of whichis rotatably supported on the cylinder 11 piston rod with the aid ofbolt 19, is at its other end rotatably supported on shaft 9. An abutmentring 20 is rotatably attached to the cylinder 11 piston rod with the aidof the above-mentioned bolt 19. When pressure from the cylinder 10causes lifting arm 8 to rotate about shaft 9, pressure arm 18 issimultaneously caused to rotate about shaft 9, so that cylinder 11 willremain at rest and follow lifting arm 8 until the latter has turned sofar that the abutment ring 20 on the cylinder 11 piston rod abutsagainst the abutment screw 21 fixed to the carriage 1, as shown in FIG.3, and the piston rod is pressed into the cylinder 11, upon which oilwill flow out from the cylinder 11 via a choke valve 22 and hose 13 toreturn to the tractor 2 hydraulics.

Cylinder 10 turns the lifting arm 8 and thus the plough frame 5 furtheruntil the center of gravity of the plough frame 5 passes a vertical linethough shaft 9, after which both the weight of the plough frame 5 andthe cylinder 10 will turn the lifting arm 8 further until the cylinder10 has traversed its full length of stroke, having turned approximately110 degrees, and the abutment ring 14 on its piston rod departs from theabutment screw 16, as shown in FIG. 4.

The weight of the plough frame 5 will turn the lifting arm 8 furtherwith the cylinder 11 as counter-force, as the oil which is pressed outof cylinder 11 is choked by choke valve 22 before flowing onward throughflowline 13 to return to the tractor 2 hydraulics. The lifting arm 8turns onward in this way until the piston rod is completely pressed intocylinder 11 and the plough frame 5 rests against the abutment screw 21on the carriage 1, as shown in FIG. 5.

Because a choke valve 23 is also provided between the cylinder 10 andthe hydraulic line 12, and because both the cylinders 10, 11 and thepressure arms 17, 18 are mutually identical and installed symmetricallyin relation to lifting arm 8, it will be apparent without further adothat, when plough frame 5 is to be turned in the reverse direction, i.e.from the working position shown in FIG. 5 to the working position shownin FIG. 2, this occurs in the same way as described above, but in thereverse sequence.

On the carriage 1 of the semi-reversible plough are attached twoidentical, double-acting hydraulic steering cylinders 24, 25 which areconnected in parallel with the reversing cylinders 10, 11 as shown inFIG. 6, and which thereby are automatically arranged to adjust the backwheel 4 to the correct position upon reversing the plough, and hold theback wheel in place during ploughing. When reversal of the plough isinitiated by pressurizing reversing cylinder 10 or 11, respectively, thetwo double-acting hydraulic steering cylinders 24, 25 willsimultaneously be pressurized, as shown in FIG. 6, and traverse theirfull length of stroke in opposite directions and steer the back wheel 4from one extreme position to the opposite extreme position.

Any pause in the reversal of the plough from a working position equal to0 degrees to approximately 90 degrees will cause the weight of theplough frame 5 to apply pressure to the same side of the hydraulicsystem as was the original pressure side, so that the back wheel 4 isheld in its new position.

Upon a pause in the reversal between approximately 90 and 110 degrees,the weight of the plough frame 5 will apply pressure to the originalreturn side of the hydraulic system, and steering cylinders 24, 25 willreturn to the position they had before the reversal started, and thusswing the back wheel 4 back again, as return oil from the steeringcylinders 24, 25 enters into the reversing cylinder 10, respectively 11,which was pressurized when reversal started, and consequently thisreversing cylinder will turn lifting arm 8 further until steeringcylinders 24, 25 have returned to their original position, or untillifting arm 8 has rotated to approximately 110 degrees and the initiallyactivated reversing cylinder 10, respectively 11, has traversed its fulllength of stroke. This causes no pressure build-up and consequentialunfortunate effects on the reversing mechanism, because the oil quantityin the hydraulic system is constant, because the reversing cylinders 10and 11 are single-acting.

Upon a pause in the reversal between approximately 110 and approximately180 degrees, corresponding to accomplished reversal, the weight of theplough frame 5 will act on the reversing cylinders 10, 11 and applypressure to the original return side of the hydraulic system, and thispressure will propagate via steering cylinders 24, 25 to originalpressure side of the initially activated reversing cylinder 10,respectively 11, but because the initially activated reversing cylinder10, respectively 11, has traversed its full length of stroke, thispressure will not move the steering cylinders 24, 25, because return oilfrom these cannot enter into the initially activated reversing cylinder10, respectively 11, because this has already traversed its full lengthof stroke. This also locks the movement of steering cylinders 24, 25.

Because not only reversing cylinders 10, 11 but also pressure arms 17,18 are mutually identical and are installed directly onto lifting arm 8and symmetrically in accordance with the invention, an ideal reversingfunction is achieved with a minimum of components.

Because reversing cylinders 10, 11 are single-acting, they only provideforce in the direction in which one wishes to reverse, and only duringthe first part of the reversing operation, so that only the weight ofthe plough frame 5 and in part the weight of the reversing mechanismrest against the abutment screw 16, respectively 21, with a minimum ofmechanical forces resulting.

The single-acting reversing cylinders 10, 11 cause no undesirablepressure build-up even if the reversing operation is interrupted.

The compact reversing mechanism according to the invention providesminimal distance between the plough and the tractor, which again yieldstechnical ploughing benefits.

It will be apparent without further ado that the reversing mechanismaccording to the invention can be utilized with advantage for otherpurposes than that described in the above-mentioned example ofexecution.

I claim:
 1. A hydraulic reversing mechanism for a reversible ploughcomprising:(a) a plough frame; (b) a lifting arm having first and secondends, said first end being connected to said plough frame; (c) a shaftattached to said second end of said lifting arm; (d) first and secondhydraulic cylinders, each having a first end attached to said first endof said lifting arm, and each having a piston rod movably disposed at asecond end thereof; and (e) first and second pressure arms rotatablyattached at a first end to said first and second piston rods,respectively, and rotatably at a second end to said shaft; (f) third andfourth hydraulic cylinders connected in parallel with said first andsecond hydraulic cylinders, respectively, for adjusting the position ofa rear wheel of said plough frame as a function of the position of saidfirst and second hydraulic cylinders; (g) whereby said first hydrauliccylinder initiates rotation of said lifting arm by extending said firstpiston rod from a retracted position to an extended position, andwhereby said second hydraulic cylinder completes rotation of saidlifting arm by retracting said second piston rod from an extendedposition to a retracted position.
 2. The hydraulic reversing mechanismof claim 1, further comprising first and second abutment means disposedon said plough frame such that said first ends of each of said first andsecond pressure arms contact said first and second abutment means,respectively, upon a first and second predetermined amount of rotationof said lifting arm.
 3. The hydraulic reversing mechanism of claim 1,wherein each of said piston rods are of a length sufficient to rotatesaid lifting arm at least approximately 90° upon moving from a fullyretracted position to a fully extended position.
 4. The hydraulicreversing mechanism of claim 1, wherein each of said piston rods are ofa length sufficient to rotate said lifting arm approximately 110°. 5.The hydraulic reversing mechanism of claim 1, wherein each of saidpiston rods are of a length sufficient to rotate said lifting armbetween approximately 90° and 110°.
 6. The reversing mechanism of claim1, wherein said first and second hydraulic cylinders are single-actinghydraulic cylinders.
 7. The reversing mechanism of claim 1, wherein saidthird and fourth hydraulic cylinders are double-acting hydrauliccylinders.